All of my prior applications and patents above identified disclose certain features of energy conversion systems adapted to increase the efficiency of energy conversion, particularly the efficiency of conversion of energy of gaseous fuels such as natural gas; and all of said prior applications and patents disclose certain heat exchanger devices adapted to increase the efficiency of heat transfer from the products of combustion of petroleum fuels, especially natural gas, to fluids, particularly liquids such as water. In all of said prior applications and patents heat exchanger devices are disclosed and such devices are arranged to provide for indirect heat transfer from the products of combustion to the liquid or other fluid to be heated by means of heat exchangers in which conditions are established providing for cooling of the combustion products to a temperature below the dew point, in order to utilize the large amount of BTU's released upon condensation of the water vapor present in the products of combustion.
The present application also contemplates highly effective recovery of the BTU's by establishing conditions which will reduce the temperature of the products of combustion to a temperature below the dew point, before discharge of the gaseous products of combustion. The present invention, however, is concerned with a combination of a number of improvements and features adapted to obtain a high efficiency while at the same time, making possible simplification of the heat exchange equipment used, as herein disclosed, reducing production costs and time, together with the elimination of certain production problems.
Before proceeding with more detailed description of the structural embodiments and features and advantages of the operation of systems according to the present invention, it is here first pointed out that while certain aspects of the invention are adaptable to use with a variety of fuels, the invention is especially adapted to the use of flammable gases, particularly natural gas, but others may be used including methane, the L.P.G. fuels, synthetic gases or even hydrogen. Moreover, while the equipment and heat exchangers provided according to the invention are adapted to the heating of a variety of fluids, either liquid or gaseous, the invention is particularly well suited to the transfer of the available BTU's of the products of combustion to liquids, solar fluids and especially to the heating of water. For these reasons, the description given hereinafter refers to the utilization of the available BTU's in natural gas in the heating of water, but it is to be understood that these references are not to be construed in a limited sense.
One of the important objects of the present invention is the provision of a water heater employing a special combination of features including a combustion chamber and heat transfer passages through which the hot combustion gases or products of combustion flow in a downward direction, while at the same time, the conditions of heat transfer are established so as to reduce the temperature of the products of combustion to or below the dew point, provision further being made for downward delivery under the action of gravity of the condensate formed, thereby avoiding the necessity for the condensate and the flue gases to flow in the flue gas passages in opposite directions to each other. In accomplishing the foregoing, the present invention preferably utilizes a blower effecting forced downward flow of the products of combustion from the combustion chamber through flue gas passages.
It is also contemplated according to the present invention to employ tubes for flow of the fluid to which the heat is being transferred in the equipment; and preferably, in accordance with the present invention, those tubes comprise externally finned tubes, desirably arranged in groups or superimposed planes, with appropriate headers providing for circulation of the fluid being heated in counterflow relation to the direction of flow of the gases.
According to the invention, it is contemplated that the heat exchanger be arranged to provide for reduction in the temperature of the products of combustion down to a point substantially below the dew point. This is desirable in order to recover the latent heat of condensation, but the development of the condensate results in the presence of certain acids having corrosive influence with respect to common types of metals employed in heat exchangers. In view of this, the invention contemplates employing highly acid-resistant metals or surface treating or coating of the metals to impart high acid resistance.
In the preferred embodiment according to the present invention, the heat exchange device comprises means defining a vertically extended flow space for combustion products, with a gaseous fuel supply and means for effecting combustion of gaseous fuel and air in the region of an upper portion of said flow space and for delivery of the combustion products downward from the upper portion of said flow space. In a typical embodiment provided for the heating of water, the water flow spaces are preferably arranged in the region at the lower portion of the gas flow space and desirably comprise a plurality of superimposed layers of finned water tubes; and an exhaust manifold and sump is provided below the finned tubes. A blower is also provided for effecting downward flow of the products of combustion through the flow space for the combustion gases and between the finned tubes, into the exhaust manifold and sump, for discharge therefrom.
This downward flow of the combustion gases, together with the provision for cooling of the gases to a temperature below the dew point, is of importance because it provides for downward drainage of the condensate from in the same direction as the downward flow of the combustion gases. This system avoids the necessity for gas and condensate flow taking place in the same passages in opposite directions.
Still further, the invention contemplates means responsive to increase in the temperature of the water above a predetermined value to shut off the blower and also shut off the gaseous fuel supply.
The invention also provides a novel form of gas and air admission means associated with the combustion chamber and providing increased efficiency in the intermixture of the gas and air being admitted into the combustion chamber.
The invention also contemplates a system of automatic controls of novel form, as will be pointed out more fully hereinafter.
Still further, the invention contemplates the employment of a novel form of automatic gas discharge damper which is particularly adapted for use in combination with the downward flow of the flue gases as above described, and serves to prevent convection induced upward flow or draft, resulting in waste of BTU's.
How the foregoing objects and advantages are attained, together with others which will be more fully developed hereinafter, will be more fully apparent from the following description referring to the accompanying drawings.